I bought a 'Bone' creeper a couple weeks ago.
formatting link
It's a great product and a dream to use. I recommend it highly.I noticed that it shared a design issue with other brands of creeper, though. If I was oriented a few degrees more or less than 'normal' in relation to the street, it would try to steer me headfirst down my driveway ramp and into the sidewalk.
This was way more excitement than I wanted, so I replaced the pivoting casters on the 'head' end of the creeper with non-pivoting type. I used a 1/2" button head screw to attach each caster and a smaller screw to hold wheel alignment after adjustment.
formatting link
It is now much safer to use on the ramp. I can now easily maneuver and hold at any angle from -90 to +90 degrees in relation to 'street normal'.--Winston